Control system for aircraft turbosuperchargers



May 1, 1945.

D. R. SHOULTS 2,374,708

CONTROL SYSTEM FOR AIRCRAFT TURBOSUPERCHARGERS Filed July 25, 1942 2Sheets-Shet 1 Fig.1.

Inventor: David RShoults,

May 1, 1945. D. R. sHouL'rs CONTROL SYSTEM FOR AIRCRAFTTURBOSUPERCHARGERS Filed July 25, 1942 2 Sheets-Sheet 2 Inventor: DavidRShoults,

b5 jya/m La/1 1 His Attorneg.

Patented May I 1945 CONTROL SYSTEM FOR AIRCRAFT TURBO- SUPERCHARGERSDavid R. Shoults, Schenectady, N. Y., assignor to General ElectricCompany, a corporation of New York Application July 25, 1942, Serial No.452,294

r 11 Claims.

The present invention relates to turbosuperchargers for aircraft andespecially to turbosuperchargers wherein the turbosupercharger isoperated by exhaust gases from an aircraft internal combustion engineand the air compressed by the turbosupercharger is used to superchargethe engine. Turbosuperchargers of this' type are regulated bycontrolling a waste gate valve which regulates the flow of exhaust gasesfrom the internal combustion engine to the supercharger.

The object of my invention is to provide an improved control systemforsuchturbosuperchargers, and for a consideration of what I believe to benovel and my invention, attention is directed to the followingspecification and to the claims appended thereto.

In the drawings, Fig. l is a diagrammatic view of a control systemembodying the invention, and

Fig. 2 is a similar view of a modification.

Referring to the drawings, l indicates an aircraft internal combustionengine having an intake manifold 2 and an exhaust manifold 3, and. 4indicates a carburetor having its outlet connected to the intakemanifold by a conduit 5. Exhaust manifold 3 is connected by a conduit 6to a nozzle box 1 of an exhaust gas-driven supercharger. The turbinewheel of the supercharger is indicated at 8 and the compressor at 9.Connected with nozzle box 1 is a waste conduit in which is located anadjustable waste gate valve [I used in regulating the turbosupercharger.On the shaft of valve IIv is fixed an arm I 2 for use in positioning thevalve and connected to arm I2 is a spring [3 which biases valve II toopenposition. Connected to the inlet of compressor 9 is an intakeconduit M for conveying air from the slip stream of the aircraft, to thecompressor, To this end, conduit l4 may be connected with a suitable ram(not shown) which faces into the slip stream of the aircraft. Thedischarge side of compressor 9 is connected by a conduit I5 to the inletof carburetor 4. In conduit I5 is an intercooler l5.

The arrangement so far described is a known one and is to be taken astypical of any suitable turbosupercharger installation. In operation,

gases from the aircraft engine are supplied through conduit 6 to nozzlebox I from which they are discharged through a ring of nozzles toturbine wheel 8 or through waste conduit 10 directly to atmosphere. Whenwaste gate valve H is wide open, substantially all the exhaust gasesdischarge directly to atmosphere, little if any passing through thenozzles to the turbine wheel. This represents no load on thesupercharger. As

waste gate valve II is gradually closed, back pressure is built up innozzle box I, effecting a gradually increasing flow of exhaust gasesthrough the nozzles to the turbine wheel to operate the supercharger.Maximum load on the supercharger is reached when waste gate valve I I isfully closed so that all gases from the engine are discharged againstthe turbine wheel. Ordinarily, waste gate valve H is in an intermediateposition, part of theexhaust gases being discharged to atmosphere andthe remainder passing through the turbine wheel.

My invention has to do particularly with an improved means forregulating waste gate valve ll.

Waste gate valve II is positioned by a fluid motor comprising a cylinderIS in which is located a piston I'I having its, stem l8 pivotallyconnected to arm I2 by a link l8. Connected with cylinder IE on oppositesides of piston I! by conduits l9 and 20 is a pilot valve comprising acasing 21 in which are located the pilot valve heads 22 and 23. Fluidpressure from any suitable source is supplied to the pilot valve by aconduit 24. The discharge pipes for the pilot valve are indicated at .25and 26. The stem 21 of the pilot valve is pivotally connected to anintermediate point on a floating lever 28. One end of floating lever 28is pivotally connected to a movable abutment 29 of. a regulator member Awhich is responsive to the absolute pressure of the air supplied by thesupercharger to the carburetor, i. e., to the discharge pressure of thesupercharger. The regulator comprises a flexible bellows 30 which at oneend is connected to movable abutment 29- and at the other end to a fixedhead 3|. tension spring 32, the upper end of which is attached to theinner end of a rod 33 which extends through head 3l and has a nut 34 onits outer end. By turning the nut 34, the tension of spring 32 may beadjusted. -The interior of bellows 30. is connected by a conduit 35 tothe inlet of the carburetor, the connection being in advance of thecarburetor throttle valve as re- Attached to movable abutment 29 is agards the direction of the flow of air to the carburetor. Connected tothe underside of movable abutment 29 are two concentric bellows 36 and31, the lower ends of which are connected to a fixed head 38. Bellows 36and 31 define two concentric spaces 39 and 40. The space 39 is evacuatedand the space v4|! is connected to the space inside bellows 36 by anopening 4| through movable abutment 29, Normally, the pressures insidebellows 30 and inside bellows 31 are equalized by reason of the opening4| andsince annular space 39 is evacuated, the regulator normallyresponds to the absolute pressure on the discharge side of thecompressor. At, 42 are adjustable stops for limiting the movement ofabutment 29 in each direction.

The other end of floating lever 28 is connected by a link 45to a movableabutment 46 of a second regulator member B which is arranged to beresponsive to the ratio between the inlet and discharge pressures ofcompressor 9. Connected with the upper side of movable abutment 46 aretwo concentric bellows 41 and 48 which define concentric spaces 49 and50. Space 49 is evacuated. Space 56 is connected by'a conduit to thecarburetor inlet, the connection being in parallel with conduit 35. Theupper ends of bellows 41 and 48 are each connected to a fixed head 52.Connected to the lower side of movable abutment 46 are two concentricbellows 53 and 54 which define concentric spaces 55 and 56. The lowerends of bellows 53 and 54 are connected with a fixed head 51. The space55 is connected by a conduit 58 with the, intake of compressor 9. Space56 inside bellows 54 is connected with space 56 inside bellows 48 by anopening 59 through movable abutment 46. 6B and 6| are adjustable stopsfor limiting the movement of movable abutment 46 in each direction.Normally, the movable abutment rests against stop 66.

The pressures in spaces 50 and 56 are normally equalized by reason ofthe opening 59. Bellows 48 is larger in diameter than bellows 54 so thatthere is a difierential area in space 50 upon which the pressure thereinacts downwardly on movable abutment 46, sucharea being equal to thedifference in area between bellows 48 and 54. In other words, there isan effective area comprising area of space 50 minus area of space 56upon which the pressure on the discharge side of the compressor isapplied to the abutment 46 in a downward direction. This is opposed bythe absolute compressor intake pressure acting upwardly on abutment 46over an area equal to the area of space 55. This area 55 divided by area56 minus area 56 is the ratio of the areas which are subjected to thecompressor inlet and discharge pressures. This ratio is made tohave avalue equal to the maximum ratiodesired between the compressor inlet anddischarge pressures.

In connection with the fluid motor, I preferably provide an arrangementwhereby, in case the fiuid pressure fails, the waste gate valve will bemoved to wide open position. To this end, conduits I9 and 26 areconnected by a by-pass conduit ID in which is located a valve casing 62provided with a valve head 63 normally'biased toward the left hand endof the casing by a spring 64. The left hand end of thevalve casing is inis closed. If the fluid pressure fails, spring 64 will move valve-head63 toward the left, thus connecting conduits I9 and 20 directly togetherthrough conduit 16. Thus, the opposite sides of cylinder I6 are directlyconnected together, permitting spring I3 to move waste gate valve II toits wide open position. At 63 is a pressureequalizing piston head forbalancing the pressure on the adjacent face of head 63 and at 64 is'adrain pipe for draining fluid pressure from casing 62.

The operation is as follows. Assume that the aircraft is in the air andis flying at an altitude lower than the critical altitude of thesupercharger, i. e., at an altitude below the maximum for which thesupercharger is designed to maintain a predetermined pressure on thedischarge side of the compressor, for example, sea level pressure. Alsoassume that at such altitude, waste gate valve is in a partially closedosition and the supercharger is operating at a speed such that thedesired pressure obtains on the discharge side of the supercharger.Under these conditions, waste gate valve II will be under the directcontrol of regulator member A, the movable abutment of regulator memberB being in engagement with stop 68. If now the pressure on the dischargeside of compressor 9 increases, movable abutment 29 will be loweredagainst the action of spring 32 thus lowering the pilot valve to admitfluid pressure beneath piston I1, thus raising the piston and openingsomewhat waste gate valve l I to decrease the speed of the superchargerand bring the pressure back to normal. On the other hand, if thepressure on the discharge side of the compressor decreases, then spring32 will eiiect an upward movement of abutment 29, thus raising the pilotvalve to admit fluid pressure 'to the upper end of cylinder I6, thuslowering piston I I to move waste gate valve I l toward closed positionwhereby the speed of the supercharger is increased to bring the pressureback to normal.

It will be noted that bellows 30 is connected to the carburetor inletand hence-responds to changes in pressure on the discharge side of thecompressor while the control of the supercharger i5 efiected byadjusting waste gate valve II. To efiect stable operation, I providemeans whereby the control member A comprising bellows 3|] responds torate of change of carburetor inlet pressure. This means comprises thepressure equalizing space 40 connected with the interior of bellows 30by opening 4|. When a change in pressure takes place at the carburetorinlet, it is transmitted to the interior of bellows 30, acting onmovable abutment 29. The effect of such change in pressure on themovable abutment is to some extent counteracted or modified by reason ofleakage through opening 4|, the amount depending upon the rate of changein pressure. With a slow ,rate of change in pressure at the carburetorinlet, a larger proportion of the change is counteracted by reason ofleakage through opening 4| than is the case with a more rapid rate ofchange. Thus, a more rapid rate of change produces a more rapid andgreater movement of the regulating valve I I than does a slower rate ofchange.

The eil'ective pressure on abutment 29 tending to cause it to move isarea of bellows 38' multiplied by the pressure, P1, in bellows 30 minusthe area of bellows 31 multiplied by the pressure, P2, in space 40inside bellows 31. This efiective pressure is opposed by spring 32.Normally; P1

and P2 are equal and with a slow rate of change, they may remain equaldue-'to the equalizing effect of opening 4| However, with a more rapidrate of change, P1 andPz become temporarily unequal, the leakage throughopening 4I being then not sufiiciently rapid to equalize them with theresult that the'efiective force tending to move abutment 29 is greaterthus producing a greater and more rapid movement of the abutment.

The size of opening 4! and thearea of bellows 46 are so chosen as togive the needed counteracting or modifying effect to provide stablegoverning.

' II. When the ratio between the compressor outlet pressure and thecompressor inlet pressure exceeds a predetermined high value, the totalefiective pressure on the upper side of abutment 46 becomes greater thanthat on the lower side whereupon abutment 46 moves downward away fromstop 60 and the differential control member B takes the control awayfrom the control member A and functions to hold a constant ratio orpressure across the supercharger compressor. If the ratio increases,abutment 46 is moved downward, lowering the pilot valve to effect anopening movement of waste gate valve I I to lower the supercharger speedto bring the ratio back to the desired value,'and vice versa. Similarly,in connection with the control member c'omprising movable abutment 46, Iprovide a counteracting or modifying means whereby the regulatorresponds to rate of change in the'pressure ratio. This is efiected bymeans of the counteractin or modifying bellows 54 and its connectionwith the interior of bellows 48 through opening 59, the operation beingin substance the same as that already described in connection withcontrol member A. With a slow rate of change in pres: sure ratio, alarger proportion. of the change is counteracted by reason of escape ofpressure through opening 59 than is the case with a more rapid rate ofchange. The size of opening 59 and the area of bellows 56 is chosen togive the needed counteracting or modifying efiect to provide stablegoverning.

In Fig. 2 is shown another modification of myinvention. Theturbosupercharger may be the same as that shown in Fig. l and the samereference numerals have been appliedto corresponding parts.

The arm I2 n the waste gate valve is connected to the stem 65 of a fluidactuated motor, the cylinder of which is indicated at 66, the piston at61, and the pilot valve at 68. The stem of the pilot valve is pivotallyconnected to one end of a floating lever 69 which is pivotally connectedby a link II to an intermediate point of a floatin lever I2. The lefthand end of lever .12 is pivotally connected to the movable abutment I3of a regulator member C which is responsive to the absolute pressure ofthe air supplied by the supercharger to the carburetor, i. e., to thedischarge pressure of the supercharger. The regulator member 0 comprisesa flexible bellows I4 which at one end is connected to movable abutmentI3 and at the other end to a fixed head 15. Attached to movable abutment13 is a tension spring 16, the upper end of which is attached to theinner end of an adjustable stud 11 which extends through support 15 andhas a nut 18' on its outer end. By turning the nut 78, the t'ensionofspring 16 may be adjusted. The interior of bellows I4 is connected by aconduit" to the inlet of the carburetor, the connection being in advanceof the carburetor throttle valve as regards direction of the flow of airto the carburetor. Connected to the under side of movable abutment I3 isa bellows 80, the lower endof which is connected to a fixed head 8|. Thespace within bellows 80 is evacuated. With this arrangement, theregulator member C responds to the absolute pressure )1]. the dischargeside of the supercharger. At 8!! are adjustable stops for limiting themovement of abutment 13 in each direction.

The other end of floating lever 12 is pivotally connected to a movableabutment 82 of a second regulator member D which is arranged to beresponsive to the ratio between the discharge and inlet pressures ofcompressor 9. Connected tothe upper side of movable abutment 82 are twoconcentric bellows 83 and 84 which define concentric spaces 85 and 86.Space 86 is evacuated.

inlet. The upper ends of bellows 83 and 84 are each connected to a fixedhead 88. Connected to the lowerside of movable abutment 82 is a bellows89, the lower end of which is connected to a fixed abutment 90 and theinterior of which is connected-by a conduit 9| to the intake ofcompressor 9. At 94 is a stop for limiting the movement of abutment 82in one direction. Normally, the movable abutment rests against stop 94.With the foregoing arrangement, abutment 82 is subjected on its underside to the compressor inlet pressure over an area equal to that ofbellows 89 and it is subjected On its upper side to the pressure on thedischarge side of the compressor over an area equal to the area ofbellows 83.

Thus, the regulator member D is responsive to the ratio between thedischarge and inlet pressures of compressor 9 and when this ratioexceeds a predetermined value determined by the ratio between the areaof bellows 83 and the areaof bellows 89, movable abutment 82 will bemoved Fig. 2 is as follows.

downward away from stop 94.

The other end of floating lever 69 is pivotally connected to a movableabutment 95 located between two bellows 96 and 97 which are supported attheir outer ends by, fixed heads98 and 99,

' respectively. In movable abutment 95 is a port lllll which connectsthe interiors of bellows 96 and 91. The interior of bellows 91 isconnected by a conduit IOI to the discharge side of the compressor 9.The interior'of bellows 96 is connected by a conduit I02 to the interiorof a bellows I03 which at one end is supported by a fixed head I04 andat the other end is provided with a movable head I which is rigidlyconnected to stem 65 of the fluid actuated servo motor. Due to port I00,the interiors of bellows 9'1, 96 and I83 are all subjected to thepressure on the discharge side of compressor 9, and under normalconditions, the pressures in them are equalized.

The operation of the arrangement shown in Assume that the aircraft is inoperation at an altitude lower .than the critical altitude of thesupercharger, that waste the pressure.

gate valve II is in' a partially closed position, and that thesupercharger is operating at a speed such that the desired pressureobtains on the discharge side of the supercharger. Under theseconditions, waste gate valve II will be under the direct control ofregulator member C, the movable-abutment of regulator member D being inengagement with stop 94. If now the pressure on mediary of link I! andfloating lever 69, admit-. ting actuating fluid to the lower side ofpiston 61, thus raising the piston and opening somewhat waste gate valveH to effect a decrease in the speed of the supercharger to bring thepressure back to the desired value. In a similarway, if the pressure onthe discharge side of compressor 9 decreases, the pilot valve is raisedto admit fluid pressure above piston 61 to effect a movement of thewaste gate valve toward closed position, thus increasing the speed ofthe supercharger to bring the pressure back to'the desired value. inresponse to the absolute pressure on'the discharge side of compressor 9to egulate the waste gate valve to maintain such pressure constant.

Movable abutment 95 is a means responsive to the rate of change on thedischarge side of compressor 9 which functions to stabilize the control.The interior of b'ellows 91 is subjected to the pressure on thedischarge side of compressor 9 the same as is the interior of bellowsl4, and

a change in such discharge pressure tends to 1 move abutment 95 the sameas it tends to move abutment 13. An increase in pressure tends to moveabutment 95 upward while a decrease in pressure tends to efiect amovement of it downward. The extent to which abutment 95 is moved bysuch a change in pressure depends upon the rate at which the change inpressure takes place, this result being effected by port I00. If theThus, the regulator member C operates the pilot valve. Upward movementof the pilot valve admits fluid pressure to cylinder 66 above piston 61,effecting a downward movement. of

piston 61- and a closing movement of wastegate valve II. Again,.the.extent of the movementofv abutment 95 depends upon the rate of change ofj the pressure on the discharge side of compresso 9 in the manneralreadyfexplained.

The function of bellows 103 is to act as a :01-

low-up or restoring mechanism for the pilot pressure in the systemcomprising bellows I conduit I02 and bellows 96. .This increase to.

pressure acts on abutment 95, lowering it an raising the pilot valve torestore it toward a posation where theflow of actuating fluid incylinder,

,66 is shut off. Similarly, a downward-movemen rate of change is slowenough so that leakage through port I00 maintains the pressure onopposite sides of abutment 95 equalized, no movement of the abutmentwill take place. However, with a more rapid rate of change, thepressures on opposite sides of abutment 95 will become unequal, theamount of the unequalization and hence the amount of the movement of theabutment depending upon the rate of change.

Assume, for example, a rapid rate of increase in pressure on thedischarge side of the compressor which calls for a rapid openingmovement of waste gate valve H. The increase in pressure effects alowering of the left hand end of floating lever I2 which effects adownward movement of the pilot valve. At the same time, upward movementof movable abutment 95 similarly effects a downward movement by thepilot valve so that the movement .of the pilot valve effected byabutment I3 is augmented by the movement effected by abutment 95, thelatter movement depending upon the rate of change in This effects agreater and more rapid movement of piston 61 to move waste gate valve lltoward open position.

Similarly, a decrease in pressure on the discharge side of thecompressor, which calls for a closing movement of waste gate valvel I,effects an upward movement of movable abutment l3,

thus raising the pilot valve and at the same time effects a downwardmovement of movable abutment 95, augmenting the upward movement of.

of piston 61 distends bellows I03, thus lowering the pressure in bellowsI03 and bellows 95to effect an upward movement of abutment 95 which inturn effects a lowering movement of the pilot' valve to restore ittoward normal position in which. the flow of actuating fluid is cut .offto the cylinder. In each case, the extent of the restoring action isdependent upon the rate of movement of piston 51 due to leakage throughport I00 after the manner already explained.

When the ratio between the discharge pressure and the inlet pressurereaches a predeterminedhigh value, the pressure on movable abutment 82reaches a value such that the abutment is moved away from stop 94whereupon the control member D, which corresponds to control memberratio of discharge pressure to inlet pressure of the compressor afterthe manner described inconnection with Fig. 1. operation of controlmember D, the rate ofchange device comprising movable abutment 95 andthe follow-up or restoring device comprising bellows I03 functions inthe manner already described in connection with control member C tocause. the ratio control device D'to function in accordance with therate of change of the ratio.

By my invention, I am enabledto obtain close stabilized regulation ofthe turbosupercharger.

At the same time my improved apparatus is,

simple in construction and reliable in operation.

In accordance with the provisions of the patent statutes, I havedescribed'the principle of operation of my invention, together with theapparatus which I now consider to represent the best-embodiment thereof,but I desire to have it understood that the apparatus shown is onlyillustrative and thattheinvention may be carried .ing the movableabutment to saidvalve means to In connection with the efl'ect regulatingmovements thereof, means subjecting said movable abutment to thepressure on the discharge side of said compressor, and means foraccelerating the effective action of said pressure on said movableabutment responsive to rate of change of said pressure.

2. The combination with a turbosupercharger comprising a gas driventurbine, a compressor, and valve means for regulating the supply of asto the turbosupercharger, of a control mechanism for sad valve meanscomprising a movturbine, of control mechanism for said valve meanscomprising a movable abutment, means connecting the movable abutment tosaid valve means to effect regulating movements thereof, meanssubjecting said movable abutment to the pressure on the discharge sideof said compressor, a second movable abutment, means connecting saidsecond movable abutment to said valve means to eflect regulatingmovements thereof,

means subjecting said second movable abutment to a pressure proportionalto the ratio of the pressures on the discharge and inlet sides of thecompressor, and means for accelerating the efi'ective action of saidpressures on said movable abutments responsive to rate of change of saiddischarge pressure and said pressure ratio, respectively.

4. The combination with a turbosupercharger comprising a gas driventurbine, a compressor and valve means for regulating the supply of gasto the'turbosupercharger, of a control mechanism for said valve meanscomprising a movable abutment, means connecting the movable abutment tosaid valve means, means for subjecting said movable abutment to thepressure on the discharge side of the compressor to eil'ect controlmovements of said movable abutment,

pressure, and restoring means for said pilot element actuated inresponseto movement of said valve means.

6,. The combination with a turbosupercharger comprising a gas driventurbine, a compressor and valve means for regulating the supply of gasto the turbine, of control mechanism for said valve means comprising aservo-motor and pilot valve for moving the valve means, a movable memberconnected to the pilot valve, pressure means responsive to a pressurecreated by said turbosupercharger for effecting movement of said movablemember, and pressure means actuated by movement of said servo-motor forsetting up a pressure which effects a restoring movement of said pilotvalve proportional to the rate of movement of said servo-motor.

7. In combination, a turbosupercharger adapted to be actuated by exhaustgases from an internal combustion engine, regulating means for theturbosupercharger, and means responsive to a pressure appurtenant to anoperating condition of the turbosupercharger and to a pressureproportional to a rate of change, of a pressure. appurtenant to anoperating condition of the turbosupercharger for positioning saidregulating means.

8. In combination, a turbine driven compressor adapted to be actuated byexhaust gases from an internal combustion engine for supplying air tothe engine, valve means for regulating the .flow of exhaust gases to theturbine,'and means directly responsive to the pressure on the dischargeside of the compressor, to the ratio of the discharge and inletpressures, and to the rateof change of said discharge pressure and saidratio for positioning said valve means.

9. In combination, a turbine driven compressor adapted to be actuated byexhaust gases from an internal combustion engine for supplying air tothe engine, valve means for regulating the flow of exhaust gases to theturbine, and means and means for accelerating the effective action of Isaid pressure on said movable abutment responsive to rate or charge ofsaid discharge pressure.

5. The combination with a turbosupercharger comprising a gas driventurbine, a compressor and valve means for regulating the supply of gasto the turbosupercharger, of a control mechanism for said valve meanscomprising a movable abutment, means including a servo systemhavresponsive to the pressure on the discharge side of the compressor,to the ratio of discharge and inlet pressures, to the rate of change ofsaid dis- 7 la'ting pressure appurtenant 'to an operating conditionotsaid turbine driven compressor.

' 11. In combination, a turbine driven compressor adapted to-be actuatedby exhaust gases 'from an internal combustion engine for supplying airto the engine, valve means for regulating the flow of exhaust gases totheturbine, and means responsive to the pressure on the discharge sideof the compressor, to the rate of change of said discharge pressure, andto the rate of movement or said valve means for positioning said valvemeans.

' DAVID R. SHOULTS.

